<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="app">
{{arr}}
</div>

</body>
<script src="../node_modules/vue/dist/vue.js"></script>
<script>
   let vm =  new Vue({
        el: '#app',
            data:{
                arr:[1,2,3]
            }
    })
//  vm.arr.push(1)
    vm.arr = vm.arr.map(item => item+1)
</script>
</html>